FPGA Code (Verilog)

Location: Code/fpga/

Key Files: - drum_trigger_top.sv - Top-level module integrating Arduino and MCU SPI slaves, system clock generation (3MHz), and status LEDs - arduino_spi_slave.sv - SPI slave interface for receiving 16-byte packets from Arduino, implements CS-based protocol and clock domain crossing - spi_slave_mcu.sv - SPI slave interface for providing data to MCU, implements clock domain crossing and test mode - TIMING_CONSTRAINTS.md - Complete timing analysis and CDC documentation

Code Structure:

Code/fpga/
├── drum_trigger_top.sv      # Top-level integration
├── arduino_spi_slave.sv     # Arduino SPI slave
├── spi_slave_mcu.sv         # MCU SPI slave
├── bno085_controller.sv      # Sensor controller
└── spi_master.sv            # SPI master (if used)

MCU Code (C)

Location: Code/mcu/ or Code/Code_for_C_imp/

Key Files: - main.c - Main application code with SPI master implementation - STM32L432KC_SPI.c - SPI peripheral driver - STM32L432KC_SPI.h - SPI peripheral header - STM32L432KC_GPIO.c - GPIO configuration - STM32L432KC_RCC.c - Clock configuration

Code Structure:

Code/mcu/
├── main.c                   # Main application
├── STM32L432KC_SPI.c       # SPI driver
├── STM32L432KC_SPI.h       # SPI header
├── STM32L432KC_GPIO.c      # GPIO driver
└── STM32L432KC_RCC.c       # Clock driver

Arduino Code

Location: Code/Nuk_Option/Arduino/arduino_sensor_bridge/

Key Files: - ARDUINO_SENSOR_BRIDGE.ino - Main Arduino code - BNO085 sensor interface via I2C (using Adafruit_BNO08x library) - SPI master implementation for FPGA communication (100kHz, Mode 0, MSB first) - 16-byte packet formatting with header (0xAA), Euler angles, gyroscope data, and flags - CS pin: D10 (FPGA_SPI_CS) - connects to FPGA arduino_cs_n input

Code Structure:

Code/Nuk_Option/Arduino/
└── arduino_sensor_bridge/
    └── ARDUINO_SENSOR_BRIDGE.ino  # Main Arduino code

Testbenches

Location: Code/test/ or Code/e155-lab7-main/fpga/sim/

Key Files: - Testbenches for individual modules - Integration testbenches - System-level testbenches

FPGA: Top-Level Module

File: Code/fpga/drum_trigger_top.sv

Description: Integrates both SPI slave interfaces and manages data flow between Arduino and MCU. This is the entry point for the FPGA design.

Key Features: - Dual SPI slave configuration - Data buffering and routing - Status LED outputs - Reset and clock management

FPGA: Arduino SPI Slave

File: Code/fpga/arduino_spi_slave.sv

Description: Implements SPI slave interface for receiving 16-byte packets from Arduino. Handles CS-based protocol, data shifting, and packet validation.

Key Features: - SPI Mode 0 (CPOL=0, CPHA=0) - 16-byte packet reception - Header validation (0xAA) - Error detection

FPGA: MCU SPI Slave

File: Code/fpga/spi_slave_mcu.sv

Description: Implements SPI slave interface for providing sensor data to MCU. Passes raw 16-byte packet buffer directly to MCU (transparent bridge).

Key Features: - SPI Mode 0 interface (read-only mode, ignores MOSI) - Clock domain crossing from FPGA system clock to MCU SCK domain - Continuous snapshot update when CS is high (transaction inactive) - Test mode support (outputs known test pattern when enabled) - Passes through raw packet buffer without modification

MCU: Main Application

File: Code/mcu/main.c

Description: Main application code for STM32 MCU. Configures SPI master, reads data from FPGA, and processes sensor data.

Key Features: - SPI1 master configuration - Sensor data reading - Quaternion processing - Application logic

MCU: SPI Driver

File: Code/mcu/STM32L432KC_SPI.c

Description: Low-level SPI peripheral driver for STM32L432KC. Handles register configuration and SPI transactions.

Key Features: - SPI peripheral initialization - SPI transaction functions - Interrupt handling (if used) - Error handling

Arduino: Sensor Bridge

File: Code/Nuk_Option/Arduino/arduino_sensor_bridge/ARDUINO_SENSOR_BRIDGE.ino

Description: Arduino code that reads BNO085 sensor via I2C and transmits data to FPGA via SPI.

Key Features: - BNO085 I2C interface (400kHz, using Adafruit_BNO08x library) - Quaternion to Euler angle conversion - SPI master implementation (100kHz, Mode 0, MSB first, CS pin D10) - 16-byte packet formatting: Header (0xAA), Roll/Pitch/Yaw (int16_t scaled by 100), Gyro X/Y/Z (int16_t scaled by 2000), Flags, Reserved - 100Hz sensor update rate (10ms intervals)

Verilog Commenting

Module Header:

/**
 * Module Name
 * Brief description of module purpose
 * 
 * Key features:
 * - Feature 1
 * - Feature 2
 * 
 * @param param_name Description
 */

Inline Comments: - Explain complex logic - Document state machine transitions - Clarify timing requirements - Note any design decisions

C Commenting

Function Header:

/**
 * Function Name
 * 
 * Brief description of function purpose
 * 
 * @param param_name Description
 * @return Description of return value
 */

Inline Comments: - Explain register configurations - Document SPI protocol details - Clarify data format conversions - Note timing requirements

Code Formatting

• Indentation: Consistent 2 or 4 spaces (maintained per file)
• Naming: Descriptive names following language conventions
• Structure: Logical organization with clear separation of concerns
• Documentation: Comments explain “why” not just “what”